Process for casting material under pressure

ABSTRACT

This disclosure provides a process for casting material under pressure into an article, such as a die or the like, having a cavity of a desired shape formed in it. Basically, the process comprises the steps of: providing molten material that is to be cast into an article in a container; skimming slag from a surface of the molten material; inserting into the container a plunger carrying a master of a shape which is to be impressed into the surface of the material, with a sufficient space being provided between the plunger and the container to cause a portion of the material to be displaced by the plunger into the space; cooling the material to cause the displaced material to form a fluidtight seal between the plunger and the container; and further inserting the plunger under pressure into the container to impress the shape into the surface of the cooled material. The present disclosure is also directed toward the product that is produced by this process.

United States Patent 1 O Connor Apr. 9, 1974 1 PROCESS FOR CASTING MATERIAL UNDER PRESSURE 211 Appl. No.: 273,786

[52] US. Cl 29/527.6, 164/80, 164/120, 164/134, 164/321 [51] Int. Cl, 823p 23/04, B22d 27/12 [58] Field of Search 164/113, 120, 319, 321, 164/80, 134; 29/5276 56] V References Cited 7 UNITED STATES PATENTS 1,956,907 5/1934 Miller et a1. 164/120 1,938,257 12/1933 Jones 164/120 3,270,383 9/1966 Hall et al. 164/120 2,716,792 9/1955 Kroyer 164/120 2,381,625 8/1945 Stewart i 164/80 X 2,932,865 4/1960 Bauer l 164/113 3,613,768 10/1971 Awano et a1... 164/120 3,254,377 "6/1966 Morton 164/312 FOREIGN PATENTS OR APPLICATIONS 161,100 6/1964 U.S.S.R, 164/319 2,036,585 12/1970 France 164/134 45/31,067 10/1970 Japan 164/134 Primary Examiner.1. Spencer Overholser Assistant Examiner.lohn E. Roethel Attorney, Agent, or FirmHarry B. ODonnell, III

[ 5 7] ABSTRACT This disclosure provides a process for casting material under pressure into an article, such 'as a die or the like, having a cavity of a desired shape formed in it. Basically, the process comprises the steps of: providing molten material that is to be cast into an article in a container; skimming slag from a surface of the molten material; inserting into the container a plunger carrying a master of a shape which is to be impressed into the surface of the material, with a sufficient space being provided between the plunger and the container to cause a portion of the material to be displaced by the plunger into the space; cooling the material to cause the displaced material to form a fluid-tight seal between. the plunger and the container; and further inserting the plunger under pressure into the container to impress the shape into the surface of the cooled material. The present disclosure is also directed toward theproduct that is produced by this process.

PROCESS FOR CASTING MATERIAL UNDER PRESSURE BACKGROUND OF THE INVENTION This invention relates to casting and, more particularly, to a process for casting material under pressure into an article, such as a die or the like, having a cavity of a desired shape formed in it, and to the product produced by that process.

In the past, various unsuccessful attempts have been made to cast molten material into a die having a cavity of a desired shape therein that was of sufficient quality to be used in molding items made of compounds of elastomers, plastics and the like.

Because of this lack of success in casting, it has heretofore been necessary to form the cavities in such dies by cold working a piece of solid material, as by cutting in the cavity of the desired shape with machines such as lathes, mills, etc. Such machining has been both lengthy and costly and must be followed up by manually rubbing the cavity surfaces to a smooth finish with abrasives. In an effort to overcome this great expense, renewed attempts have been made at casting, wherein molten material has been held in a container that mounts amaster of the desired cavity shape that can be plunged into the molten material under pressure. Heretofore, however, such attempts at pressurized casting have been fraught with problems of impracticality and safety, because the pressurized molten material would squirt out between the plunger outer periphery and the container interior.

Co-pending, commonly-owned U. S. Pat. application Ser. No. 227,383, filed Feb. 18, 1972, provides apparatus which overcomes the aforenoted problems that have heretofore been encountered with pressurized casting and enables successful casting of molten material into a die having a cavity of a desired shape therein which is of sufficient quality for use in moldingitems made of compounds of elastomers, plastics and the like and, thus, eliminates the aforenoted previously required expensive machining and abrading operations.

SUMMARY OF THE INvaNTioN The present invention'provides aprocess for casting material under pressure into an article, such as a die or the like, having. a cavity of a desired shape formed in it. Basically, the process comprises the steps of:' providing molten material that is to be cast into an article in a container; skimming slag from a surface of the molten material; inserting into the container a plungercarrying a master of a shape which is to be impressed into the surface of the material, with a sufficient space being provided between the plunger and the container to press the shape into the surface of the cooled material. The present invention is also directed toward the product that is produced by this process.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in the accompanying drawings, wherein: 7

FIG. 1 is a perspective view of a form of a product that can be produced by the process of the present invention;

F IG. 2 is a somewhat schematic elevational perspective view showing a form of apparatus that can be utilized in performing the novel process of the present invention;

FIG. 3 is an enlarged sectional view taken generally along line 3-3 of FIG. 2;

FIGS. 4, 5 and 6 are fragmentary schematic views illustrating the relationship of the plunger, container and stripper means of the apparatus of FIG. 2 in different conditions of the operation of the: apparatus shown in FIGS. 2 and 3;

FIG. 7 is a sectional view taken along line 77 of FIG. 3; 7

FIG. 8 is a greatly enlarged schematic view illustrating in detail the construction of the plunger and container of the apparatus shown in FIGS. 2-7; and

FIG. 9 is a schematic diagram of presently preferred control means that can be employed with the apparatus shown in FIGS. 2-7.

DETAILED DESCRIPTION Referring now to the drawings, and more particularly to FIG. 1 thereof, there is illustrated a typical product, an article, such as a die l0, having a cavity 11 of a desired shape formed in it, which can be produced in accordance with the novel process that is provided in accordance with the present invention. While it should be understood that various means could be employed, FIGS. 2-9 of the drawingsillustrate a form of apparatus 12 that has been used with good results in carrying out the novel process of the present invention to produce the product 10. I

As illustrated in FIGS. 2-9, the presently preferred formof the apparatus (12 comprises a container 13 for holding moltenmaterial that is to be cast into an article, such asthe die 10 or the like, having a cavity, such as the cavity 11, of a desired shape formed therein; and a plunger 14 mounted for movement into and out of the container 13 and mounting an embossed master 15 of the desired shape of the cavity that can be impressed into the molten material.

As further shownin FIGS. 2-9, the apparatus 12 includes a rectangular base member 17 which is adapted to be generally horizontally arranged on a surface such as a table top or the like (not shown). Projecting upwardly from each of the four corners of the base memcause a portion of the material to be displaced by the plunger into the space; cooling the material to cause the displaced material to form a fluid-tight seal between the plunger and the container; and further inserting the plunger under pressure into the container to imber 17 are four uprights 18 which, in turn, support a rectangular top plate 19 and interconnect it to.the. base member 17. The top plate 19 is provided with a central opening 20 through which downwardly passes a reciprocably movable piston rod 21 of a fluid motor drive means, such as a so called hydraulic cylinder motor or the like 22, which has its cylinder 23 fixed to the top plate 19 by suitable fastening means, such as welding or the like. The lower end of the piston rod 21 is connected, as by threads 24, to the top of the plunger 14, which also, has the master shape 15 removably fastened, as by threads 25, to the radial center of its bottom surface. The container 13 is in the form of a cup which has its lower exterior surrounded by an electrically powered resistance heater 26 that is, in turn, supported on the base member 17 such that the radial centers of the container 13 and the plunger-carried master shape 15 are axially aligned with one another.

As best shown in FIGS. 2, 3 and 8-9, the heater 26 is connected across a pair of electric power lines L and L in electrical series with a normally open switch 28 by conductors 29 and 30. The upper end of the piston rod 21 of the fluid motor drive means 22 carries a piston 31 that is contained within the cylinder 23. The interior portion of the cylinder 23 below the piston 31 is fluid connected by a first conduit 32a to a first outlet port 3314 of a multiposition control valve 33, whereas the interior portion of the cylinder 23 above the piston 31 is connected by a second conduit 32d, which also includes a pressure gage 32g, to a second outlet port 33d of the valve 33. The valve 33 has its single inlet port 33i connected to a source of pressurized fluid (as shown in block in FIG. 9) by a third conduit 34. Coolant can be supplied to a hollow space 14s provided in the interior of the plunger 14 from a source of pressurized coolant (also shown in block in FIG. 9) that is connected to the plunger interior space 14s in series with a gate valve 14v through a coolant supply conduit 14i, and a drain conduit 14d is also provided for discharging the coolant from the plunger hollow space 14s.

With the foregoing arrangement, a solid billet s (FIG. 4) of the material that is to be cast into the die '10 (FIGS. 1 and 6) can be placed'into the container cup 13 (FIG. 4) and then be changed into its molten state 10m (FIG. 5) through energization of the heater 26 by closure of the switch 28. The plunger 14 and the master shape carried by it can be moved into and out of the container 13 through operation of the multiposition control valve 33. For example, movement of the plug cock 33c of the control valve 33 to a first position (shown in solid lines in FIG. 9) fluid connecting the valve inlet port 33i to the first outlet port 3314 will supply pressurized fluid to the bottom of the piston 31 and cause upward movement of the plunger 14 toward movement'out of the container cup 13, whereas movement of the plug cock 330 to a second position (shown in shadow in FIG. 9) fluid connecting valve inlet port 33i to a second outlet port 33d (and thus also concurrently disconnecting the first outlet port 3311 from the inlet port 33i) will cause pressurized fluid to be supplied to the top of the piston 31 and thus cause the plunger to be moved downwardly toward the container cup 13.

As further illustrated in FIGS. 2-9 and as shown in particular detail in FIG. 8, the container 13 is in the form of a cup, the interior of which includes a generally horizontal bottom wall having side walls extending upwardly therefrom, while the plunger 14 hasthe shape of a truncated cone. In accordance with the present invention, it has been found particularly advantageous to form the interior of the container 13 and the exterior & 6), good results have been obtained by employing a container 13 and a plunger 14 which were both made of carbon steel and by using downward tapers offset from the vertical at an angle 0 of about 3 on the tapered exterior of the plunger 14 and offset from the vertical at an angle a of about l/2 on the upstanding tapered sidewalls of the interior of the container cup 13 (FIG. 8). The diameters of the tapered exterior of the plunger 14 and the tapered interior of the container 13 were made to provide a l/4-inch annular space S therebetween when the plunger 14 was inserted into the container 13, and the embossed master shape 15 was machined from No. 303 Stainless Steel.

To cast an article, such as the die 10, by the novel process of the present invention with the apparatus 12, an operator first moves the plug cock 33c of the control valve 33 to its first position (FIG. 9 solid lines) directing pressurized fluid through the valve inlet 33i, outlet 33a, conduit 32a and against the bottom of the drive means piston 31 causing the plunger 14 to be moved upwardly out of and well above the container cup 13.

Next, the previously machined embossed master 15 of the desired shape of the cavity 11 is affixed to the bottom center of the plunger 14 by threads 25. Then, the billet of the solid material 10s that is to be formed into the die 10 is placed into the container 13 (FIG. 4) and changed into its molten state 10m (FIG. 5) by energization of the heater 26 through closure of the switch 28. During the early part of this melting step, the plunger 14 and the master shape 15 which is now attached to it are moved close to the top of but not into the container cup 13 by rotating the valve plug cock 33c to its second position (FIG. 9 shadow lines) directing pressurized fluid through the valve inlet 33:, outlet 33d, conduit 32d and against the top of the piston 31. As shown in FIG. 4, this will cause the lower tip of the master shape 15 to be engaged with the top of the billet of solid material 10s and result in preheating of the attached master shape 15 to substantially the temperature of the molten'mate rial 10m. It should, of course, be understood that the master 15 might be so pre heated by other means, such as with other. heater means (not, shown).

Just when the billet of solid material 10s is changed to its molten state 10m, the plug cock 33c isretumed to its first position (FIG. 9 solid lines) raising the plunger 14 and its attached master shape 15 away from the container 13 sufficiently to permit the operator to skim slag from the top of the moltenmaterial 10m. As soon. as this slag has been skimmed, the operator returns the valve plug cock 33c partly towards its second position (FIG. 9 shadow lines).partially redirecting the pressurized fluid against the top'of the piston 31 and inserting the plunger 14 and its attached master shape 15 into the container cup 13, which now holds the molten material 10m just far enough (e.g;, 7/8 inch) to cause a portion of the molten material 10m to be displaced by the thus inserted plunger 14 into the annular space S between its tapered exterior and the tapered interior of the container 13.

The heater 26 is now immediately de-energized by opening the switch 28 and the'molten material m is allowed to cool sufficiently to cause that portion thereof which has been displaced into the annular space S between the tapered exterior of the partially inserted plunger 14 and the tapered interior of the container 13 to resolidify sufficiently to provide an annular ring R which forms a fluid-tight seal between the plunger 14 and the container 13.

Next, the operator moves the valve plug cock 33c fully into its second position (FIG. 9 shadow lines) fully directing the pressurized fluid against the top of the piston 31 and further inserting or ramming the plunger 13 and its attached master shape into the container cup 13 under pressure and causing the master to be impressed into the upper surface of the material. Escape of any of the pressurized material from between the plunger 14 and the container 13 is prevented by the integral annular ring R which provides a fluid-tight seal therebetween. The now pressurized and shapeimpressed material is allowed to cool in the container until fully resolidified into the die 10, having the cavity 11 formed therein. This cooling and resolidification is preferably further promoted by opening the coolant valve 14v to supply coolant to the plunger hollow space 14s.

it is then necessary to separate the resolidified and cast die 10 from the container 13, the plunger 14 and the master shape 15 which, following resolidification of the material forming the die 10, are all stuck together. In accordance with the present invention, the separation of these parts is facilitated by providing theapparatus 12 with mechanical stripping means. 7

As illustrated, these stripping means include two sets of diametrically opposed stripperrods 35 and 36 that are suspended from the top plate 19 of the apparatus 10. The first set of stripper rods 35 are horizontally spaced apart from one'another such that they will engage the container 13 but will not engage the plunger 14 nor the resolidified cast die 10 upon upward movement of the stuck together container 13, plunger 14, and master shape 15 by movement of the plug cock 33c to its first position (FIG. 9 solid lines). The second set of stripper rods 36 are angularly offset from, and ex tend downwardly from the top plate 19 a lesser distance than, the first set of stripper rods 35 and are horizontally spaced apart from one another such that they will engage the top of the integral annular seal means ring R at the top of the resolidified and cast die '10 but will not engage the container 13 nor the plunger 14 upon upward movement of the then stuck together container 13, plunger 14, and master shape 15 by rotation of the plug cock 330 to its first position (FIG. 9 solid lines). With this arrangement (as best shown in FIG. 6), the container 13 will be engaged by the first set of stripper rods 35 and stripped free from the bottom and sides of the resolidifiedand cast die 10, while the top of the integral annular seal means ring R will be engaged by. the second set of stripper rods 36' and stripped free from the tapered exterior of the upwardly moving plunger 14 and will, in turn, strip the top of the resolidified and cast die 10 free from the bottoms of the master shape 15 and the plunger 14. Then, the integral annular seal means ring R (FIGS. 1 & 6) can be readily removed (FIG. 1) from the top of the strippedreso'liditied and cast die 10 asby tool means such as a grinder,

lathe or the like (notshown).

By employing the novel process of the present invention as described above, a single machined mastershape, such as the embossed master shape 15, can be used many times to cast a plurality of articles, such as the die 10, having a cavity of that desired shape, such as the cavity 11, formed therein that is of sufficient quality to be used in molding compounds made of elastomers, plastics and the like. Thus, machining costs can be tremendously reduced.

It should be apparent that while there has been described what is presently considered to be a presently preferred form of the present invention in accordance with the Patent Statutes, changes may be made in the disclosed process and product produced thereby without departing from the true spirit and scope of this invention. For example, other equivalent forms of apparatus might be substituted for the illustrated apparatus 12. Also, various other materials might be utilized for the material to be cast or for the materials of construction of the container 13, plunger 1.4, and master shape 15.

What is claimed is:

1. A process for casting an article, such as a die and the like, having a cavity of a desired shape formed therein, comprising the steps of:

a. providng molten material that. is to be cast into an article in acontainer; skimming slag from a surface of said molten material; V

c. inserting into said container 21 plunger carrying a master, which has been preheated substantially to the temperature of said molten material, of a shape which is to be-impressed into said surface of, said material with a sufficient space being provided between said plunger and said container. to causea portion of said material to be displaced by said plunger into said space; cooling said material to cause said displaced material to form a fluid-tight seal between said plunger and said container; and

e. further insertingsaid plunger under pressure into said container to impress said shape into said surface of said cooled material.

2. The invention of claim 1, further including cooling said plunger following said step of further inserting said plunger under pressure into said container.

3. Theinvention of claim 2, further including stripping saidarticle free from said container after said material has had said shape impressed into said surface ping said article'free from said plunger after said material has had said shape impressed intosaid surface and been allowed to solidify.

5. The invention of claim 4, furtherincluding removing said displaced seal-forming material from said stripped article.

6. The invention of claim 5, wherein the exterior of said plunger and the interior of said container are formed with tapers.

7. The invention of claim 2, further including stripping said article free from said plungerafter said material has had said shape impressed into said surface and been allowed to solidify. t

8. The invention of claim 1, wherein the exterior of said plunger and the interior of said container are formed with tapers.

t a: a: 1* 

1. A process for casting an article, such as a die and the like, having a cavity of a desired shape formed therein, comprising the steps of: a. providng molten material that is to be cast into an article in a container; b. skimming slag from a surface of said molten material; c. inserting into said container a plunger carrying a master, which has been preheated substantially to the temperature of said molten material, of a shape which is to be impressed into said surface of said material with a sufficient space being provided between said plunger and said container to cause a portion of said material to be displaced by said plunger into said space; d. cooling said material to cause said displaced material to form a fluid-tight seal between said plunger and said container; and e. further inserting said plunger under pressure into said container to impress said shape into said surface of said cooled material.
 2. The invention of claim 1, further including cooling said plunger following said step of further inserting said plunger under pressure into said container.
 3. The invention of claim 2, further including stripping said article free from said container after said material has had said shape impressed into said surface and been allowed to solidify.
 4. The invention of claim 3, further including stripping said article free from said plunger after said material has had said shape impressed into said surface and been allowed to solidify.
 5. The invention of claim 4, further including removing said displaced seal-forming material from said stripped article.
 6. The invention of claim 5, wherein the exterior of said plunger and the interior of said container are formed with tapers.
 7. The invention of claim 2, further including stripping said article free from said plunger after said material has had said shape impressed into said surface and been allowed to solidify.
 8. The invention of claim 1, wherein the exterior of said plunger and the interior of said container are formed with tapers. 